import java.util.Random;

public class random_alpha {
    public static void main(String[] args) {
        //随机生成字母1
        char []chs=new char[52];
        for(int i=0;i<chs.length;i++)
        {
            if(i<=25)
            {
                chs[i]=(char)(97+i);//a-z
            }
            else{
                chs[i]=(char)(65+i-26);//A-Z,因为前面跑了26要减掉
            }
        }
        String result="";
        //2
        Random r=new Random();
        for(int i=0;i<4;i++) {
            int randomIndex = r.nextInt(chs.length);
        result=result+chs[randomIndex];
        }

        int number=r.nextInt(10);
        result+=number;
        System.out.println(result);
    }
}
